Top water officials in Nevada, Arizona and California have negotiated a deal to cut their use of the Colorado River and slow the decline of Lake Mead, but the landmark agreement is far from finished.

Negotiators from Arizona and California are now shopping the plan to various water users and policymakers in their states, where the proposed cuts are likely to be painful and in some cases unprecedented. Arizona would shoulder most of the reductions, but the tentative deal marks the first time California has agreed to share the pain — if the drought worsens.